In machines of this kind, when workpieces of different lengths are being machined, the two headstocks which jointly receive, clamp and drive the workpiece must be moved against or relative to each other in order for the workpiece to be clamped at its end to the extent possible. In this connection, it is necessary that each tool holder slide associated with a headstock must also be moved for it to be at the necessary distance from the headstock when machining of the workpiece starts.
For the displacement of these two machine units on each machine bed half, there have been known and used spherical roller spindles drivable by servomotors in order to be able to move the respective machine unit. Long spherical roller spindles not only require a high cost for their manufacture but also present difficulties with respect to their protection against fouling by coolants and chips while being used in the machine. Also, rack and pinion drives have been employed, which again are susceptible to dirt and involve a correspondingly high expense when using covers and protective devices.
It is an object of the invention to develop a center drive machine so that the headstock and the tool holder slide of each machine bed half are displaceable by means of a simple drive system and are, moveover, controllable in a simple manner.